21919217 has 4 divisors (see below), whose sum is σ = 23072880. Its totient is φ = 20765556.

The previous prime is 21919213. The next prime is 21919223. The reversal of 21919217 is 71291912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21919217 - 2² = 21919213 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21919213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 576803 + ... + 576840.

It is an arithmetic number, because the mean of its divisors is an integer number (5768220).

Almost surely, 2^21919217 is an apocalyptic number.

It is an amenable number.

21919217 is a deficient number, since it is larger than the sum of its proper divisors (1153663).

21919217 is a wasteful number, since it uses less digits than its factorization.

21919217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1153662.

The product of its digits is 2268, while the sum is 32.

The square root of 21919217 is about 4681.7963432853. The cubic root of 21919217 is about 279.8605470541.

The spelling of 21919217 in words is "twenty-one million, nine hundred nineteen thousand, two hundred seventeen".